1. Field of the Invention
The invention relates to a lens structure, a light source device, and a light source module. Particularly, the invention relates to a lens structure, having a free-form surface and total internal reflection surfaces, a light source device, and a light source module using the same.
2. Description of Related Art
A total internal reflection (TIR) collimator lens is generally used in a lighting system to collect a light beam from a light source, so as to achieve a specific irradiation angle and improve uniformity of the projected light. Generally, the TIR collimator lens includes an upper surface, a lower surface, and a TIR cup surface connected to the upper surface and the lower surface. Regarding a light beam that forms a larger included angle with an optical axis of the light source, it is refracted to the TIR cup surface by the lower surface, then reflected to the upper surface by the TIR cup surface, and leaving the TIR collimator lens through the upper surface. Regarding a light beam that forms a smaller included angle with the optical axis of the light source, it is directly refracted to the upper surface by the lower surface, and leaving the TIR collimator lens through the upper surface. The TIR collimator lens could effectively concentrate the light beam and reduce a light emitting angle of the light beam, so that the light beam could be effectively transmitted to a desired object.
However, in an existing TIR collimator lens, the upper surface, the lower surface, and the TIR cup surface are generally rotationally symmetric to the optical axis of the light source, so that a shape of the light projected by the existing TIR collimator lens is generally a rotationally symmetric pattern, for example, a circle, etc. In this way, if a region to be lighted is a rectangular region, for example, an advertising billboard, the existing TIR collimator lens has following shortages. FIG. 1A illustrates a situation that a light beam passing through the existing TIR collimator lens is projected on a rectangular target object. Referring to FIG. 1A, a light spot 10 is formed when the light beam passes through the existing TIR collimator lens and projects on a rectangular target object 200, and the light spot 10 is not easy to cover four corners of the target object 200, so that uniformity of the light beam projected on the rectangular target object 200 is poor. FIG. 1B illustrates a situation that a light beam passes through another existing TIR collimator lens and projects on a rectangular target object. Referring to FIG. 1B, considering the uniformity, the light spot covers the four corners of the target object 200, though a part of the light beam overflows from four sides (i.e. regions Z) of the target object 200, which may cause poor efficiency of the light beam in lighting the target object 200. FIG. 2 illustrates a situation that a light beam passes through the existing TIR collimator lens and projects on a rectangular target object. Referring to FIG. 2, in an application of lighting a billboard, a light source is generally disposed at a lower edge of the rectangular target object 200, and the TIR collimator lens 30 has to be tilted by a certain angle in order to light the whole rectangular target object 200. Since illuminance per unit area is inversely proportional to a square of a distance between the light source, illuminance on a region a that locates further from the light source 30 is far smaller than illuminance on a region b that locates closer to the light source 30, so that the uniformity of the light beam projected on the rectangular target object 200 is poor. Moreover, a part of the light beam overflows from an upper edge B of the rectangular target object 200, which decreases the efficiency of the light beam in lighting the target object 200.
Moreover, devices or components related to a light source system are also provided. For example, Taiwan Patent Publication No. 201105902 discloses a reflector, and a part of the reflector surrounds a light emitting diode (LED) module, and light usage efficiency of the LED module is increased through the reflector. Moreover, Taiwan Patent Publication No. 201032359 discloses a lens having a light incident surface, a light emitting surface, a first side surface, and a second side surface. U.S. Pat. No. 7,891,835 discloses a shielding device having a reflection surface for guiding a light beam to a predetermined side. U.S. Pat. No. 7,854,536 discloses an apparatus including LEDs and an optical device, where a reflector is configured between the LEDs and the optical device. U.S. Pat. No. 7,637,630 discloses a shielding device, which guides a light beam emitted from an LED device. U.S. Pat. No. 7,674,018 discloses a lens, where a light beam emitted from an LED is incident through one region of the lens and exits from another region of the lens. U.S. Pat. No. 5,757,557 discloses a lens having a front surface and a side surface, and a light beam emitted from a light source is reflected by the side surface to emit via the front surface.